11
1. Thermostat control (MSZ)
Thermostat turns ON or OFF by the difference between room temperature and set temperature.
2-1. COOL ( ) OPERATION
2. Indoor fan speed control
Indoor fan operates continuously at the set speed by FAN SPEED CONTROL button regardless of the thermostat’s OFF-
ON. [When the thermostat turns OFF, the indoor fan stops running to reduce power consumption.
After that, the indoor fan stops for 60 seconds and then operates at Very Low for 10 seconds to sense accurate room
temperature. The indoor fan alternates ON and OFF at this interval while the thermostat is OFF.
When the room temperature rises and the thermostat is ON, the indoor fan starts running according to the settings on the
remote controller. (
MSZ-GE60/71VA
)]
[When the thermostat turns OFF, the indoor fan operates at very Low to reduce power consumption. When the room tem-
perature rises and the thermostat turns ON, the indoor fan starts running according to the settings on the remote controller
(
MSZ-EF
)]
In AUTO, the fan speed is as follows.
3. Coil frost prevention (MSZ)
The compressor operational frequency is controlled to prevent the temperature of indoor heat exchanger from falling excessively.
The compressor is turned OFF for 5 minutes when the temperature of indoor coil thermistor continues 3°C or less for
5 minutes or more.
The indoor fan maintains the actual speed at the time.
4. Low outside temperature operation (MUZ-GC/FD/GE/EF)
MUZ-GC25
If the outside temperature falls to 17°C or less during operation in COOL mode, the unit will switch to the low outside
temperature operation mode.
Each outdoor actuator (compressor/fan/LEV) is operated in the exclusive control, which is different from one of normal cool
operation.
Especially, fan motor does not operate continuously to maintain sufficient cooling capacity.
<Operation>
(1) Outdoor fan control
Basically, outdoor unit (compressor) operates with outdoor fan OFF.
But, when any of following conditions are satisfied, the outdoor fan turns ON for about 5 seconds.
a). The defrost thermistor reads 45°C or more.
b). The fin temperature thermistor reads 60°C or more.
(2) LEV (expansion valve) control
In normal cool operation, the opening degree of expansion valve is corrected according to the discharge temperature.
But in this mode it is fixed to the value corresponding to the operation frequency of compressor.
(3) Dew drop prevention
When the ambient temperature thermistor reads -20°C or less, as coil frost or dew drop from indoor unit may occur, the
compressor turns OFF with the outdoor fan ON for prevention of it.
(4) Outdoor temperature detecting control
To detect the exact outdoor temperature in this mode, the compressor turns OFF, but the outdoor fan stays ON for
3 minutes once every 1 hour. If the outdoor temperature rises over 19°C, the unit goes back to the normal COOL mode.
If the outside temperature stays below 19°C, the unit continues to run in the low outside temperature operation mode.
MUZ-GC35, FD, GE, EF
If the outside temperature falls to 18°C or less during operation in COOL mode, the unit will switch to the low outside
temperature operation mode.
<Operation>
(1) Outdoor fan control
The outdoor fan rotation speed slows down to maintain sufficient cooling capacity.
NOTE:
Even when the unit is in the "thermostat-off" status under the low outside temperature operation mode, the
outdoor fan rotation does not stop.
(2) Dew drop prevention
When the ambient temperature thermistor reads the following temperature, as coil frost or dew drop from indoor unit
may occur, the compressor turns OFF with the outdoor fan OFF for prevention of dew drop.
• -20°C or less (
MUZ-GC35, FD25/35, GE25/35/42, EF25/35/42
)
• -15°C or less (
MUZ-FD50
)
• -12°C or less (
MUZ-GE50/60/71,EF50
)
(3) Outdoor temperature detecting control
To detect the exact outdoor temperature in this mode, the compressor turns OFF but the outdoor fan stays ON for
3 minutes once every 1 hour. If the outdoor temperature rises over about 18°C, the unit goes back to the normal COOL mode.
If the outside temperature stays below about 18°C, the unit continues to run in the low outside temperature operation mode.
Other protections work as well as in the normal COOL mode.
ON
-1°C or more
Less than -1°C
-1°C
-0.75°C
Room temperature minus
set temperature (During operation)
Room temperature minus
set temperature (Initial)
Thermostat
OFF
High
Med.
Low
1.75°C
3°C
1°C
Fan speed
Room temperature minus
set temperature (During operation)
Room temperature minus
set temperature (Initial)
Between 1 and 1.75°C
Less than 1°C
1.75°C or more
2
MSZ/MLZ MICROPROCESSOR CONTROL
